Season four continued, and greatly embellished upon, the changes to the franchise already rung in by the middle to end of season three.

"Scorpion, Part II" saw the conclusion to the season three finale and, most crucially to the future of the series, the introduction of a new character, Seven of Nine. Just a single episode later, Kes departed from Voyager, not to return until the season six episode, "Fury".

Given that the newly-introduced Seven of Nine had lots of character development to catch up on compared to the other principal actors, season four could be described as the "Seven of Nine season", being as it was, heavy with episodes centering solely on Jeri Ryan's character. Relationships between Seven of Nine and all the other main characters needed to be quickly established, and so conflict between Seven and B'Elanna Torres was introduced in "Day of Honor", and Harry Kim's infatuation with Seven became a hallmark of the season in "Revulsion". The Doctor, for so long a student under Kes' tutelage, turned teacher to Seven in "Prey", kinship with Tuvok was explored in "Hunters", and quintessential to the remainder of the series, Seven's relationship with Janeway took center-stage in "The Gift", "The Raven", "Retrospect", "The Omega Directive", and the season finale, "Hope and Fear". However, with audience figures ballooning, it appeared that the producers of Voyager had finally found a character that appealed to the crucial 16-24 year old male demographic, and at this point, nobody was complaining.

Prior to season four, story writers had given Voyager six thwarted opportunities to return to the Alpha Quadrant, aside from the series premiere "Caretaker". However, as the series continued to mature, episodes presenting the Voyager crew with the possibility of returning home were absent throughout season four, until the finale "Hope and Fear". Instead, making large jumps closer to Earth became a regular occurrence. Kes' "gift" at the start of the season provided Voyager with its first big jump (knocking 10,000 light years or 10 years off their journey), and these "jumps" would continue through the following three seasons. As a consequence, relatively few opportunities to return to Earth in one "giant leap" were presented, with season five's "Timeless", season seven's "Inside Man" and the series finale "Endgame" being notable exceptions.

Alongside this change of pace, the concept of the crew as "family", and Voyager as "home" continued to gain prominence, and script writers clearly made a conscious effort to include these references into their scripts. Examples of this can be found scattered throughout most episodes in season four.

"This ship has become our home, it's part of our family. As illogical as this sounds, I feel as close to Voyager as I do to any member of my crew. It's carried us Tuvok, even nurtured us, and right now it needs one of us."

Other notable developments in season four included the cementing of Tom Paris and B'Elanna Torres' relationship in "Day of Honor", the season three hinted at conflict with the Krenim, and the opening of Voyager's new astrometrics lab in "Year of Hell", as well as the appearance of "grey mode" in "Demon", with all Voyager's non-essential functions shut down to conserve power reserves.

However, one of the single biggest developments for the series arc as a whole occurs mid-way through the season in "Message in a Bottle", when the Doctor is transported back to the Alpha Quadrant using alien technology, and Voyager finally makes contact with Starfleet. Voyager's use of the alien technology has unforeseen consequences however, as the crew are introduced to the Hirogen, a hunting species who would re-assert themselves throughout the remainder of the season in "Hunters", "Prey", and "The Killing Game". By the end of the series, the Hirogen joined the Kazon, the Borg, and the Vidiians as one of the chosen few species to interact regularly with Voyager and contribute significantly to its overall journey.

It is fair to say that by mid-season four, the introduction of Seven of Nine, the departure of Kes, and the opening of the new astrometrics lab meant that Voyager had quickly become very different from what had gone before in the previous three seasons.